JP2019150752A - Calcium removal method and calcium removal equipment for calcium-containing waste water - Google Patents

Abstract

To provide a calcium removal method and a calcium removal facility for calcium-containing wastewater that can improve maintainability: in particular, when treating calcium-containing wastewater with a high calcium concentration, it is possible to facilitate the removal work of scales fixed to the members of a reaction tank of the calcium removal equipment, and by reducing the work frequency.SOLUTION: The method for removing calcium from calcium-containing wastewater according to the present invention introduces calcium-containing wastewater as treated water through at least one of a pipe or a predetermined tank 11, and the introduced calcium-containing wastewater is introduced into a reaction tank 12 in which the calcium-containing wastewater is reacted with carbonate to produce calcium carbonate, and a scale softening agent is added to at least one of the reaction tank 12, the predetermined tank 11, and the pipe, thereby softening the scale and facilitating its removal operation.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a calcium removal method and a calcium removal facility for calcium-containing wastewater such as leachate generated at a managed final disposal site.

  Generally, waste that cannot be reused or recycled out of waste generated in industry or general life is landfilled at a final disposal site such as a managed final disposal site. In the past, organic waste such as garbage was often directly landfilled at the managed final disposal site. However, environmental hygiene problems such as the breeding of flies, rats, and crows, and the generation of combustible gas due to the decomposition of organic matter In recent years, incineration ash and incineration fly ash that have undergone incineration have been mainly reclaimed due to safety issues such as, and the problem of reducing the amount of imported waste for extending landfill life.

By the way, acidic components such as SO _X , NO _X , and HCl that can be contained in the exhaust gas discharged from the incineration facility cause acid rain, so in the incineration facility, alkaline slaked lime powder is sprayed on the flue. The sum is eliminated. Therefore, the incinerated fly ash contains a large amount of calcium salt and unreacted slaked lime, so that the leachate generated at the managed final disposal site also has a high calcium concentration and a high pH. This is a cause of scale adhesion failure in pipes, pumps, biological treatment tanks, etc. in treatment facilities.

  FIG. 10 shows a standard processing flow of the calcium removal equipment installed in the managed final disposal site. In this method, water to be treated, which is calcium-containing wastewater, is made uniform in the adjustment tank 11, and then sodium carbonate is added in the reaction tank 12 to generate calcium carbonate. Thereafter, an inorganic flocculant is added in the flocculant tank 13, and a polymer flocculant is added in the floc forming tank 14 to remove calcium carbonate particles by agglomeration and precipitation treatment, thereby reducing the calcium concentration of the supernatant of the precipitation tank. This prevents the scale from being attached to a subsequent biological treatment tank.

  However, in the case of this conventional flow, the calcium concentration of precipitation supernatant water, which is the treated water of the calcium removal equipment, decreases, but the calcium carbonate scale adheres to the inner wall of the reaction tank 12 and the agitator shaft into which calcium carbonate is injected. In particular, when wastewater with a high calcium concentration, such as a calcium concentration of 700 mg / L or more as in recent years, or a calcium concentration of 1000 to 5000 mg / L is a target, a hard scale that cannot be easily removed As described above, various scale obstacles due to the adhesion of the ink occur, which is a big problem.

  As means for preventing this scale failure, various means have been proposed since the removal of calcium from the leachate is effective. For example, in Patent Document 1, as an example, after leaching water having a calcium concentration of 520 ppm was homogenized in a regulating tank, 1500 ppm of sodium carbonate in a reaction tank was added and stirred at pH 7 for 10 minutes, and then ferric chloride was 300 ppm in a coagulation tank. In the floc forming tank, 1 ppm of the polymer flocculant is added to perform the coagulation sedimentation treatment, the calcium concentration of the sedimentation tank supernatant water is set to 40 ppm, and the water is sent to the biological treatment facility in the subsequent stage, so In addition, a technique is disclosed in which scale does not adhere to piping and processing devices.

In Patent Document 2, as Example 1, leachate having a calcium concentration of 400 mg / L and pH 7.8 flows into a fluidized bed crystallization reaction tank filled with CaCO ₃ pellets having an average particle size of 0.5 mm. In the crystallization reaction tank, 0.1 ₂ mol / L of Na ₂ CO ₃ is added as an alkaline agent, and treatment is performed at a flow rate in the tank of 100 m ³ / m ² / hr by circulating 4 times the amount of inflow water. After the biological treatment, acid flocculation treatment, filtration treatment, activated carbon treatment, and sterilization treatment in the latter stage, the calcium concentration of the final treated water becomes 20 mg / L, and the sludge extraction piping of the flocculation settling tank is blocked, the sludge transfer piping and A technique is disclosed in which the blockage problem of pumps has been solved.

Furthermore, Patent Document 3 discloses a scale prevention technique for containing phosphonic acid and / or phosphonate and a low-molecular water-soluble polymer in an aqueous system containing an inorganic suspended substance such as calcium carbonate. As the set water quality of Examples and Comparative Examples, a calcium hardness of 300 mg-CaCO ₃ / L and a suspended calcium carbonate concentration of up to 500 mg-CaCO ₃ / L are described.

JP-A 63-258692 JP 2001-47062 A JP 2003-53389 A

  However, Patent Document 1 and Patent Document 2 can be said to be a hashing technique when the scale problem originated from the incineration ash-derived scale adhesion problem, and the calcium concentration of leachate as the problem is 400 to 520 mg / It is at a low concentration level such as L, which is different from the recent treatment of leachate containing a high concentration of calcium.

Further, even in Patent Document 3, the set water quality is a calcium hardness of 300 mg-CaCO ₃ / L and a suspended calcium carbonate concentration of up to 500 mg-CaCO ₃ / L. / L, only 200 mg-Ca / L.

  The proportion of incineration ash in the wastes brought into recent managed-type final disposal sites is increasing, and there is also a final disposal site where almost all incineration ash is incinerated. In proportion to this tendency, the calcium concentration of leachate has also increased to 700 mg-Ca / L or more, and further to a high concentration of 1000 to 5000 mg-Ca / L. In recent leachate treatment facilities, there are an increasing number of facilities having a calcium removal facility consisting of a flow of reaction tank → flocculation tank → floc formation tank → precipitation tank as in Patent Document 1 described above, and subsequent biological treatment equipment Subsequent scale problems in piping and pumps have been solved, but instead of this, scale obstacles in the reaction tank itself for removing calcium by adding sodium carbonate have become a problem.

  FIG. 11 is a photograph showing the scale adhesion of the stirrer in the reaction tank of the conventional calcium removal equipment. This stirrer has two impellers in the middle and lower stages of the shaft, but the scale with a thickness of 30 mm or more covers both the shaft and impeller, and the shaft diameter and impeller diameter cannot be judged from the appearance. It has become.

  The scale is hard and fossilized, and can only be removed with a hammer. After removing the scale, it takes about 2 to 3 weeks to reach the state shown in Fig. 11 again. If the scale is excessive, the motor will be overloaded and a power trip will occur. It has become.

  In addition, since the scale adheres not only to the stirrer but also to the inner wall and bottom of the reaction tank, it is also necessary to remove the scale by scraping it off with a scraper or the like and further performing acid cleaning. Therefore, it can be said that the calcium removal technique disclosed in Patent Document 1 cannot cope with a high concentration level such as a calcium concentration of 700 to 5000 mg / L as in recent leachate.

  In patent document 1 and patent document 2, as it is clear from the fact that scale adhesion in each reaction tank itself is not a problem, the calcium concentration targeted by these conventional techniques is as low as 400 to 520 mg / L. It is considered that this technology is only applicable to the level.

  The object of the present invention is to facilitate the removal work of scales fixed to the members of the reaction tank of the calcium removal equipment, particularly when treating calcium-containing wastewater with a high calcium concentration, and maintainability of the calcium removal equipment. An object of the present invention is to provide a calcium removal method and a calcium removal facility for calcium-containing wastewater.

  In order to solve the above problems, the present invention can be configured as follows.

(1) Calcium-containing wastewater as treated water is introduced through at least one of piping or a predetermined tank,
Introducing the calcium-containing wastewater introduced into a reaction vessel that reacts with carbonate to produce calcium carbonate;
A method for removing calcium from calcium-containing wastewater, wherein a scale softening agent is added to at least one of the reaction tank, the predetermined tank, and the pipe.

  (2) The method for removing calcium from calcium-containing wastewater according to (1), wherein the scale softening agent comprises a (meth) acrylic polymer.

  (3) The (meth) acrylic polymer is a poly (meth) acrylate, acrylic acid-methacrylic acid copolymer salt, acrylic acid-maleic acid copolymer salt, and acrylic acid-sulfonic acid monomer copolymer. The method for removing calcium from calcium-containing wastewater according to (2), comprising at least one selected from the group consisting of coalesced salts.

  (4) The method for removing calcium from calcium-containing wastewater according to (2) or (3), wherein the scale softening agent further contains at least one inorganic salt selected from iron salts and aluminum salts.

  (5) The calcium removal method of the calcium containing waste_water | drain as described in any one of (1)-(4) whose addition amount of the said scale softening agent is 10-200 mg per 1L of said calcium containing waste_water | drain.

  (6) The calcium removal method of the calcium containing waste_water | drain as described in (4) whose addition amount of the said inorganic salt is 100-200 mass parts with respect to 100 mass parts of said (meth) acrylic-type polymers.

(7) a pipe or a predetermined tank into which calcium-containing wastewater as treated water is introduced;
A reaction tank in which the water to be treated introduced through the pipe or the predetermined tank is reacted with carbonate to generate calcium carbonate;
An adding means for adding a scale softening agent for softening the scale formed from the calcium carbonate to at least one of the reaction tank, the pipe, and the predetermined tank;
A stirring means for stirring the scale softening agent added in at least one of the reaction tank and the predetermined tank;
A calcium removal facility characterized by comprising:

  (8) The addition means is added to either one or both of the treated water inflow portion of the reaction vessel and the agitator shaft wetted surface portion provided in the reaction vessel, according to (7). Calcium removal equipment.

(9) A floc-forming tank in which a polymer flocculant is further added to the water to be treated after the scale softening agent has been added and stirred to form a floc floc;
A settling tank in which the water to be treated on which the floc flocs have been formed after the addition of the polymer flocculant is agglomerated and precipitated to obtain precipitation supernatant water;
The calcium removal facility according to (7) or (8), further comprising:

  According to the calcium removal method and the calcium removal equipment of the present invention, it is possible to facilitate the removal work of the scales fixed to the members of the reaction tank of the calcium removal equipment, and to maintain the calcium removal equipment by reducing the work frequency. Can be improved. The present invention is particularly effective when treating calcium-containing wastewater having a high calcium concentration.

It is a flowchart which shows 1st Embodiment of the calcium removal method of this invention. It is explanatory drawing of the injection | pouring point (1) in the case of adding a scale softening agent to a reaction tank. It is explanatory drawing of the injection | pouring point (2) in the case of adding a scale softening agent to a reaction tank. It is explanatory drawing of the injection | pouring point (3) in the case of adding a scale softening agent to a reaction tank. It is a flowchart which shows 2nd Embodiment of the calcium removal method of this invention. It is a flowchart which shows 3rd Embodiment of the calcium removal method of this invention. It is a flowchart which shows 4th Embodiment of the calcium removal method of this invention. It is a flowchart which shows 5th Embodiment of the calcium removal method of this invention. It is a flowchart which shows 6th Embodiment of the calcium removal method of this invention. It is a flowchart which shows an example of the conventional calcium removal method. It is a photograph for demonstrating the scale condition adhering to the reaction tank stirring machine shaft of the conventional calcium removal equipment.

  Hereinafter, the present invention will be specifically described with reference to the drawings. However, the present invention is not limited to a specific example.

  FIG. 1 is a flow showing a first embodiment of the calcium removal method of the present invention. As shown in the drawing, calcium-containing wastewater (treated water) such as leachate generated in a managed final disposal site or the like is first uniformized in the adjustment tank 11. In order to make it uniform, a stirring means such as mechanical stirring is preferably used. The treated water 1 that has been made uniform is sent to the reaction tank 12.

  In the reaction tank 12, a carbonate such as sodium carbonate is added. The addition amount may be an amount conventionally used. When carbonate is added, it reacts with calcium ions contained in the water to be treated to produce calcium carbonate.

  And what is characteristic in this embodiment is that a scale softening agent is further added to the reaction tank 12. As described above, conventionally, the calcium carbonate generated in the reaction tank 12 is fixed to the inner wall and bottom of the reaction tank 12, the stirrer, the pH electrode, the piping, and the like, and a scale that is difficult to remove is formed. In this embodiment, since the scale is softened by adding the scale softening agent to the reaction tank 12, the scale removal work is facilitated, and the maintainability of the calcium removal equipment can be improved.

  The scale softening agent may be any as long as it can soften the scale formed from calcium carbonate. Examples of the scale softening agent include (meth) acrylic polymers. Specifically, polyacrylic acid, polymethacrylic acid, (meth) acrylic acid-maleic acid copolymer, (meth) acrylic acid-sulfonic acid monomer copolymer, acrylic acid-methacrylic acid copolymer, (meth ) Acrylic acid-hydroxyallyloxypropane sulfonic acid copolymer and salts thereof (sodium salt, potassium salt, etc.). As sulfonic acid monomers (sulfonic acid group-containing monomers), 2-acrylamido-2-methylpropanesulfonic acid, methallylsulfonic acid, styrenesulfonic acid, allylsulfonic acid, vinylsulfonic acid, 2-hydroxy-3-allyloxy- Examples thereof include 1-propanesulfonic acid and 2-hydroxy-3-butenesulfonic acid. Examples of other scale softening agents include polyacrylamide and hydrolysates thereof, maleic acid polymers, itaconic acid polymers, acrylamido-2-methylpropane sulfonic acid, isoprene sulfonic acid and the like. Two-component or three-component copolymers of the system. These listed compounds can be used individually by 1 type or in combination of 2 or more types. Among these, poly (meth) acrylate, acrylic acid-methacrylic acid copolymer salt, acrylic acid-maleic acid copolymer salt, and acrylic acid-sulfonic acid monomer copolymer salt are particularly preferable. In the present invention, “(meth) acrylic acid” means acrylic acid, methacrylic acid, or both.

  Although the molecular weight of the (meth) acrylic polymer is not particularly limited, for example, those having a relatively low molecular weight such as a weight average molecular weight of 2000 to 12000, preferably 3000 to 9000 are preferable.

  Moreover, it is preferable that the scale softening agent of this invention contains inorganic salts, such as iron salt and aluminum salt, in addition to said organic polymer. Thereby, the scale softening effect is further improved. Specifically, at least one selected from the group consisting of ferric chloride, polyferric sulfate (polyiron), aluminum sulfate, and polyaluminum chloride (PAC) can be used.

  When the scale softening agent contains an inorganic salt in addition to the above organic polymer, preferred combinations thereof include a (meth) acrylic acid-sulfonic acid monomer copolymer / iron salt combination, sodium polyacrylate A salt / iron salt combination and a polyacrylic acid sodium salt / aluminum salt combination are preferred.

  The required addition amount of the scale softening agent (in the case of containing the inorganic salt, the amount including the inorganic salt) is appropriately set according to the calcium concentration and the salt concentration of the water to be treated. L (10 to 200 mg per liter of calcium-containing wastewater), preferably 20 to 180 mg / L, more preferably 30 to 150 mg / L, still more preferably 40 to 130 mg / L, and most preferably 50 to 100 mg / L.

  Among these, when using inorganic salt, the addition amount of inorganic salt is 100-200 mass parts with respect to 100 mass parts of said (meth) acrylic-type polymer, Preferably it is 130-190 mass parts, Most preferably, 150- It is preferable to set it as 180 mass parts.

  As shown in FIGS. 2 to 4, the reaction vessel 12 is provided with a stirring means having a stirrer shaft 12 </ b> A and an impeller 12 </ b> B. As shown in FIG. 2, the pouring position for adding the scale softening agent in the reaction tank 12 (that is, the position of the scale softening agent adding means) is the vicinity where the water to be treated flows into the reaction tank 12 (the treatment target). The water inflow portion a-1 or the liquid contact surface portion a-2 of the stirrer shaft 12A is preferable as shown in FIG. Moreover, as shown in FIG. 4, it is good also considering both of these (a-1 and a-2) as an injection | pouring point. In particular, when injected into the agitator shaft 12A wetted surface a-2, the scale attached to the agitator shaft 12A and the impeller 12B can be effectively softened.

  As shown in FIG. 1, in this embodiment, untreated water is treated in a reaction tank 12 and then sent to a coagulation tank 13. In the flocculation tank 13, an inorganic flocculant is added to the untreated water. Examples of the inorganic flocculant include iron salts and aluminum salts, and these may be used alone or in combination of two or more.

  Next, the water to be treated that has been treated in the coagulation tank 13 is sent to the flock formation tank 14. In the floc-forming layer 14, a polymer flocculant is added. Examples of the polymer flocculant include a cationic polymer flocculant, an anionic polymer flocculant, and an amphoteric polymer flocculant. These may be used alone or in combination of two or more. Also good.

  Next, the non-processed water processed in the flock formation tank 14 is sent to the settling tank 15, and is separated into the precipitate and the supernatant water. The supernatant water whose calcium concentration has been reduced by the above treatment is sent to a subsequent biological treatment facility or the like. Thus, the calcium removal method of the present invention is completed.

  Next, another embodiment of the present invention will be described. FIG. 5 is a flowchart showing the second embodiment of the present invention. What is characteristic in the present embodiment is that the addition position of the scale softening agent is not the reaction tank 12 but the adjustment tank 11 which is a predetermined tank. Even when a scale softening agent is added to the adjustment tank 11, it is possible to soften the scale attached to the wall of the reaction tank 12, the stirrer, or the like. In addition, in this Embodiment, although the example which adds a scale softening agent to the adjustment tank 11 is shown, the addition position of a scale softening agent is piping between the adjustment tank 11 and the reaction tank 12. Also good. Moreover, another tank may be provided between the adjustment tank 11 and the reaction tank 12, and a scale softening agent may be added to the tank.

  FIG. 6 is a flowchart showing the third embodiment of the present invention. In the present embodiment, the scale softening agent is added to both the adjustment tank 11 and the reaction tank 12. By comprising in this way, the softening effect of a scale further improves.

  FIGS. 7-9 is a flowchart which shows the 4th-6th embodiment of this invention, and the coagulation tank 13 in the 1st-3rd embodiment shown in FIG.1, FIG.5, FIG.6, respectively. Is omitted, and an inorganic flocculant is added to the reaction vessel 12. In these cases, the addition position of the scale softening agent is the reaction tank 12, the adjustment tank 11, or both (reaction tank 12 and the adjustment tank 11). Even if it is such a structure, the objective of this invention can be achieved, and simplification of the calcium removal method and removal equipment is achieved by omitting the coagulation tank.

In each of the embodiments described above, the calcium concentration of the calcium-containing wastewater is not particularly limited, but the present invention can improve the maintainability due to scale formation even if the calcium-containing wastewater has a high calcium concentration. In particular, the present invention is suitably applicable when a large amount of scale is generated when processing calcium-containing wastewater having a calcium concentration of 700 mg / L or more, for example, 100 to 5000 mg / L.
In FIG. 1 to FIG. 9 according to the present embodiment, the introduction of the water to be treated has been shown as an example of introduction from the pipe (corresponding to the part →) into the adjustment tank 11, but not limited thereto, as a predetermined tank, For example, the reaction vessel 12 may be introduced directly from the piping without passing through the piping, and only the adjustment vessel 11 or the reaction vessel 12 alone. Further, the predetermined tank is not limited to the adjustment tank 11, and may be a stirring tank, a mixing tank, a storage tank, or the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited by a following example.

  In the following examples and comparative examples, the scale softening agent shown in Table 2 was used when the water to be treated shown in Table 1 was treated. Table 3 shows the injection position and injection rate of the scale softening agent.

<Comparative Example 1>
Calcium removal test by the flow of the conventional calcium removal method of FIG. 10 using an experimental apparatus consisting of an adjustment tank → reaction tank → coagulation tank → floc formation tank → precipitation tank for water to be treated as shown in Table 1 Went.

  Each condition is as follows: treated water volume 1000 L / day, sodium carbonate injection rate 5500 mg / L, polyiron injection rate 200 mg / L as an inorganic flocculant, and Ebagrose A-151 injection from Mizu Inc. as a polymer flocculant Rate 1 mg / L. The injection points of sodium carbonate, polyiron, and polymer flocculant were in the inflow draft tubes of the reaction tank, the coagulation tank, and the floc forming tank, respectively.

After 18 days from the start of treatment, clogging due to scale adhesion in the reaction vessel inflow draft tube was observed and overflow of the inflow water was observed. When the treatment was continued by brush cleaning in the draft tube, 27 days from the start of treatment. During the lapse of time, the stirrer in the reaction vessel 12 caused a current trip due to scale adhesion, and the stirrer stopped, so the processing was terminated.
After draining water, the inner surface of the reaction tank and the stirrer were observed, and a hard scale of 5 cm or more adhered to the inner wall, bottom surface, and stirrer shaft of the reaction tank. Finally, after removal work such as scraping or peeling off with a metal scraper, the residual scale was dissolved with a dilute hydrochloric acid aqueous solution to finish the cleaning work.

<Example 1>
Using the same experimental apparatus as described above, 100 mg / L of the scale softening agent 1 shown in Table 2 was injected into the injection point a-1 (see FIG. 2) of the reaction tank 12 and processed as the flow 1 of FIG. The calcium removal test was performed under the same conditions as in the comparative example.
The removal test was conducted for 5 weeks. During the period, the draft tube in the reaction vessel injection section was blocked due to scale adhesion, and no overflow of the influent occurred, and the reaction vessel agitator stopped due to current trip. The test was terminated with no continuous operation. When the inner surface of the reaction vessel and the stirrer were observed after draining water, the scale was also softened and could be easily peeled off simply by washing with light scraping with a metal scraper or the like.
In addition, the thickness of the adhesion scale of the stirrer shaft is not much different from that of the comparative example, but the softening is remarkable, and pulverization with a hammer is unnecessary, and it can be easily removed by scraping with a metal scraper. .

<Example 2>
Using the same experimental apparatus as above, except that 50 mg / L of the scale softening agent 2 shown in Table 2 was injected into the injection point a-1 and the injection point a-2 (see FIG. 4) of the reaction tank 12, respectively. Conducted a calcium removal test under the same conditions as in Example 1.

<Example 3>
Using the same experimental apparatus as described above, the scale softening agent 3 shown in Table 2 was injected at 100 mg / L at the injection point b (see FIG. 5) of the adjustment tank 11 without injecting the scale softening agent into the reaction tank 12. Then, a calcium removal test was performed under the same conditions as in Example 1 except that the treatment was performed as Flow 2 in FIG.

<Example 4>
Using the same experimental apparatus as described above, 50 mg / kg of the scale softening agent 4 shown in Table 2 was added to the injection point b (see FIG. 6) of the adjustment tank 11 and the injection point a-2 (see FIG. 3) of the reaction tank 12, respectively. A calcium removal test was performed under the same conditions as in Example 3 except that L was injected and the flow 3 of FIG. 6 was processed.

<Example 5>
The coagulation tank is bypassed from the same experimental apparatus as described above, and the addition position of the polyiron is changed to the reaction tank, and the injection points a-1 and a-2 (see FIG. 4) of the reaction tank are shown in Table 3. A calcium removal test was performed under the same conditions as in Example 2 except that 50 mg / L of the scale softening agent 3 was injected and processed as Flow 4 in FIG.

<Example 6>
Using the same experimental apparatus as in Example 5, 50 mg / L each of the scale softening agent 4 shown in Table 2 was injected into the injection point a-1 and the injection point a-2 (see FIG. 4) of the reaction tank 12 and processed. A calcium removal test was performed under the same conditions as in Example 5 except that.

<Example 7>
The scale softener was not injected into the reaction tank, but 100 mg / L of the scale softener 5 shown in Table 2 was injected into the injection point b (see FIG. 8) of the adjustment tank 11 to process as flow 5 in FIG. Except for the above, the calcium removal test was performed under the same conditions as in Example 6.

<Example 8>
The same as Example 7 except that 50 mg / L of the scale softening agent 6 shown in Table 2 was injected into the injection point b of the adjustment tank 11 and the injection point a-2 of the reaction tank 12 and processed as the flow 6 of FIG. A calcium removal treatment test was performed under the conditions.

  In any of Example 2 to Example 8, the inflow water overflow in the inflow portion draft tube of the reaction tank 12 and the current trip of the stirrer did not occur during the continuous test period of 5 weeks, and the reaction after the end of the treatment test. When the inner surface of the tank 12 and the stirrer were observed, softening equivalent to or higher than that of Experimental Example 1 was confirmed. In particular, in Example 5 and Example 6, the adhesion scales on the inner surface and the bottom surface of the reaction tank 12 were 1 cm or less in thickness, and it was possible to remove the adhesion scales only by washing the hose with pressure water.

Claims (9)

Calcium-containing waste water as treated water is introduced through at least one of piping or a predetermined tank,
Introducing the calcium-containing wastewater introduced into a reaction vessel that reacts with carbonate to produce calcium carbonate;
A method for removing calcium from calcium-containing wastewater, wherein a scale softening agent is added to at least one of the reaction tank, the predetermined tank, and the pipe.   The calcium removal method of the calcium containing waste_water | drain of Claim 1 in which the said scale softening agent contains a (meth) acrylic-type polymer.   The (meth) acrylic polymer is composed of poly (meth) acrylate, acrylic acid-methacrylic acid copolymer salt, acrylic acid-maleic acid copolymer salt, and acrylic acid-sulfonic acid monomer copolymer salt. The calcium removal method of the calcium containing waste water of Claim 2 containing at least 1 sort (s) selected from the group which consists of.   The method for removing calcium from calcium-containing wastewater according to claim 2 or 3, wherein the scale softening agent further comprises at least one inorganic salt selected from iron salts and aluminum salts.   The calcium removal method of the calcium containing waste_water | drain of any one of Claims 1-4 whose addition amount of the said scale softening agent is 10-200 mg per 1L of said calcium containing waste_water | drains.   The calcium removal method of the calcium containing waste_water | drain of Claim 4 whose addition amount of the said inorganic salt is 100-200 mass parts with respect to 100 mass parts of said (meth) acrylic-type polymers. A pipe or a predetermined tank into which calcium-containing wastewater as treated water is introduced; and
A reaction tank in which the water to be treated introduced through the pipe or the predetermined tank is reacted with carbonate to generate calcium carbonate;
An adding means for adding a scale softening agent for softening the scale formed from the calcium carbonate to at least one of the reaction tank, the pipe, and the predetermined tank;
A stirring means for stirring the scale softening agent added in at least one of the reaction tank and the predetermined tank;
A calcium removal facility characterized by comprising:   The calcium removal equipment according to claim 7, wherein the adding means adds to either one or both of the treated water inflow portion of the reaction tank and the agitator shaft wetted surface portion provided in the reaction tank. . A floc forming tank in which a polymer flocculant is further added to the water to be treated after the scale softening agent has been added and stirred, to form a floc floc;
A settling tank in which the water to be treated on which the floc flocs have been formed after the addition of the polymer flocculant is agglomerated and precipitated to obtain precipitation supernatant water;
The calcium removal equipment according to claim 7 or 8, further comprising:

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